Carrier current control system



pt. 2 9, 194 .J. WOODWORTH 2,297,380

CARRIER CURRENT CONTROL SYSTEM Filed Aug. 13, 1941 2 Sheets-Sheet l Inventor:

v John L.Wdo dwor'th,

Sept. 29, 1942. J. L. WOODWORTH 2,297,380

CARRIER CURRENT CONTROL SYSTEM Filed Aug. 13, 1941 2 Sheets-Sheet 2 Pl .2. g

' CARR/ER CURRENT RECEIVER 75- 7 I alMzrALuc- L l Fig.3

74 Q 64 Q" 75 B/METALLIG 88 11 Q 89 9 2Q (i111 Inventor: v John Lflwo'odworth,

His Attorneg.

PatenteciSept. 29, 1942 UNITED STATE 2,297,380 CARRIER CURRENT CONTBOL SYSTEM John L.

Woodworth, Schenectady, N. Y., assignor to General Electric Company, a corporation or New York Application August 13, 1941, Serial No. 406,588

This invention relates. to carrier current control systems, and more particularly to such systems in which the carrier current is utilized to effect control 0! loads on a power system at remote points.

Carrier current control systems for controlling loads on a power system at remote points generally utilize carrier current receivers at such remote loads which respond to carrier current only aiter they have received suchcarrier current for a substantial length of time. It is desirable to providethat such carrier current receivers shall not respond instantaneously to carrier current, in order to avoid possible response to transients induced on the power line by lightning,

switching operations, and the like. Although, in manufacturing such carrier current receivers which respond to carrier current only after a substantial time, eiiorts are made to manufacture all. such receivers alike, it is inevitable that certainmanuiacturing tolerances exist. Each carrier current receiver consequentlyresponds to reception of carrier current tor a slightly difierent time.

Such receivers generally operate in response to application 0! line voltage for an interval of time, and, since line voltages vary considerably in diiierent parts for normal power systems due to loading conditions and the like, the receivers respond to carrier current pulses of different duration because they are energized by voltage of diiierent intensities.

For such reasons, carrier current receivers oi the type which respond only to reception or carrier current for a substantial interval generally vary in their time of response to such carrier current by considerable amounts. For example, one type oi carrier current receiver used extensively to control water heater loads has a thermal element to which heat is applied during reception of carrier current. These carrier current controllers are manufactured so as to close the load circuit aiter receiving carrier current nominally for ten seconds. Actually, such controllers are manufactured to energize their associated load circuits after about 4 or 5 seconds. The time varies slightly due to manufacturing variations. As installed, these controllers are energized by line voltages oi different values, and, sometimes act to complete their associated load circuits in a period as short as three seconds. Others mayrequire as long as six seconds beiore they complete their associated load circuits. I

- A typical carrier current receiver, oi the Sis arranged around the second bimetallic strip described above, is described and claimed in U. S.

Letters Patent 2,064,644, 'ior Control device, issued to me on December 15, 1936, and assigned to the same assignee as the present application. This receiver is described hereinafter in connection with the description and explanation oi the operation of myinvention.

Another such carrier current controller is disclosed and claimed in my copending application for Letters Patent, Serial No. 385,278, for Carrier current controller, filed on March 26, 1941, and

assigned to the same assignee as the present application.

Briefly, this device comprises a bimetallic strip fixed at one end to a support, and at the other end to a second bimetallic strip arranged to bend in the opposite direction in response to heating. I

A movable electric circuit contact is mounted on the end of this second bimetallic strip and is arrangedto engage a fixed electric circuit con- Q tact upon motion of the second bimetallic strip caused by heating. An electrical heating winding so that upon application of electric'energy to the heater for a short period, the second bimetallic. strip flexes to close the electric contacts, while the first bimetallic strip does not bend substantially. Ii heating be continued longer, heat fiows irom the second bimetallic strip to the first by conduction, or otherwise, and causes the first bimetallic strip to flex. Flexure of this first bimetallic strip is sufficient to separate the electrical contacts even though the second bimetallic strip is bent to a very large extent.

Oflpeak loadcontrol'by using such receivers is now accomplished bytransmitting a carrier current impulse of sui'ficient duration to cause ever receiver to operate. Such operation connects the associated loads to the power-line at any desired time after the peak load for a day has decreased by a suitable amount. Such a carrier current impulse isusually transmitted to add water heater loads to a' power system after the evening to these receivers and this impulse causes them to disconnect their associated loads from the power line. In the case of the particular receivers described and claimed in the above mentioned patent and application, this impulse which produces disconnection oi the load is usually typ about 30 seconds in length.

It is, therefore, usual that the carrier current controllers will be so actuated as to keep their are connectedto the power line H, and certain ones of these loads are controlled by carrier current control receivers such, for example, as disclwed, and claimed in my aforesaid patent and;

application and described hereinafter. These carrier current controlled loads, not shown, may comprise water heaters having thermostatic control, street lighting loads, or anyother load which heaters which are thermostatically controlled,

does not cause a sudden disconnection of a large total load from the power system. This is true because such loads have generally been energized for a considerable period of time, during which many such loads have been disconnected fromthe power system by their individual thermo-- static control. However, during the period when such loads are all disconnected from the power system'by carrier control, practically all of the associated thermostatcontrols connect the loads to the power line, except for their disconnection by the carrier current receivers. When a carrier current impulse is transmitted to connect all such loads to the power system therefore, the entire carrier current controlled load is applied to the power system at one time.

It is accordingly an object of my invention to provide an improved and simplified carrier current control system having means whereby small increments of the carrier current controlled loads may be added to the power system as desired. I

It is a further object of my invention to provide an improved and simplified carrier current control system for controlling remote loads on a power system having means whereby the carrier current controlled loads may be so controlled as to maintain the power system load substantially constant except when the total system load increases beyond the point at which all carrier current controlled loads are disconnected or when the total system load decreases beyond the point where all the carrier current controlled loads are connected. It is a corollary object of my invention to provide simple and effective means whereby such control is automatically effected in response to power demands-on the system.

It is also an object of my invention to provide an improved and simplified carrier current control system having means utilizing only one control frequency whereby a plurality of remote loads may be connected and disconnected from the power system consecutively as desired in response to carrier current of such one frequency.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, both as to its organization and manner of omration, to=

gether with further objects and advantages thereof may best he understood by reference to following description taken in connection with the accompanying drawings in which Fig. 1

illustrates a carrier current control transmitter connected with a power transmission system according to my invention; Fig. 2 illustrates carrier current control receivers and associated loads connected with a power transmission systern, and Fig. 3 illustrates a thermal relay as.

illustrated in Fig. 2.

I In Fig. 1 a generator, or other alternating current power source, is represented by three slip rings and associated brushes iii to which a power line, ii is connected. Various loads, not shown,

j-suitable carrier currents and includes a motor l2 arranged to be energized from the power line H through a circuit breaker l3, and a generator l4. Thegenerator I 4 produces alternating voltage of carrier frequency, suitable for energizing the power line I I so as to operate the carrier current control receivers connected thereto. This frequency may be of the order of 400 to 1000 cycles, The generator is connected to the power line H serially through a circuit breaker l5, carrier current coupling inductances l6, and capacitors ill. The capacitors H are provided to insulate the generator II from power currents in the power line i l, and the inductances l6 are provided to resonate with the coupling capacitors l! at the carrier current frequency, so that very little reactance is presented to carrier current between the generator l4 and the power line I I.

In operation, closing of the circuit breaker l3 starts the motor l2, and subsequent closing of the circuit breaker" I 5 energizes the power line H with carrier current from the generator I. If the circuit breaker l5 be kept closed for ten seconds, assuming that carrier current control receivers are utilized which have characteristics as described above, all such receivers connect their associated loads to the power line II. If, however, the circuit breaker I5 be kept closed for thirty seconds, the. carrier current control receivers disconnect all their associated loads from the power line H.

In accordance with my invention, I provide means for maintaining the circuit breaker l5 closed for a time just'suflicient to connect any desired number of carrier current controlled loads to the power line H. In the case of the particular carrier current control receivers described above, if the circuit breaker be kept closed for three seconds, very few of the carrier cur rent control receivers connect their associated loads to the power line II. If the circuit breaker l5 be kept closed for a slightly longer time, for example, three and one-half seconds, the carrier current control receivers connect a larger number of their associated loads to the power line. By controlling the length of time which the circuit breaker l5 remains closed, the amount of load added to the system by the carrier current control receivers is adjusted to any desired value.

If at any time it bedesired to remove a portion of the carrier current controlled load from the power line H, it is only necessary to maintain the circuit breaker l5 closed for thirty seconds in order to disconnect the entire carrier current controlled load from the system. Then,

give an indication'of the power delivered by the.

system to connected loads, such indication bearing some desired" relation with the maximum power delivery capabilities of the system. For example, such demand may conveniently be measuredby a meter responsive to current flowing in the system, which meter is so constructedas to be responsivelonly to current flowing for a substantial time. 4

Such a currentmeten in which a thermal lag is provided to insure response of the meter only to current flowing for substantial periods, is described in Letters Patent No. 1,156,414, issued on October 12, 1915, to Paul M. Lincoln. It may be desired to use such a meter on certain power systerns to indicate demand, because the maximum power delivering capability of a system is generally limited by the amount or heating produced in the generating equipment and associated circuits. The demand, as measured by the meter described in the above mentioned Lincoln patent, is closely related to this maximum power delivering capability.

Alternatively, the power demand on a power system utilizing my invention may be measured by an instrument which indicates a function of power flowing in the system, in tegrated in some desirable manner with respect to time. Such a demand meter is described in Letters Patent No. 1,156,412, issued on October 12, 1915, to Paul M. Lincoln, I! such a meter'be used, the demand on the system as measured by the meter is somewhat'morebiosely related to the total system load.

In certain other situations it may be desired to utilize still another type of demand meter, commonly called a block demand meter. This type. of demand meter comprises a watt hour meter which is automatically reset to zero at the end of each block," or predetermined period.

and which indicates demand at the end of each such block, or period, according to the number of watt hours used in each such period. These periods mam-for example, be a quarter or a half hour.

Any of these types of demand meters may be utilized in accordance with my invention to provide an indication by which an operator can con trol a carrier current system according to my invention. or to provide automatic operation of remote loads by carrier current control so as to maintain the total system load substantially constant. In providing such automatic operation according to my invention, the demand meter is provided with two sets of contacts, one set 01' contacts being closed when the demand is greater than a predetermined amount somewhat less than the total power delivering capability of the system, and the other set of contacts being closed when the demand is less than a predetermined smaller amount. If the last described "block demand meter be utilized with this system, it can conveniently be arranged to operate only the first such contacts. The other set of contacts, which closes at a predetermined smaller demand, may be operated in response to the reduction of cur rent in the power lines below a certain predetermined value.

In the drawings. a rectangle i8 represents such a demand meter which may be responsive to any desired function of the power delivering capability of the system. This meter I8 is energized from the power line ll through current transformers i9 and potential transformers 20, and has a set of contacts 2| which are closed by an arm 22, made of conductive material, whenever the system demand is greater than a predetermined amount. The meter also has a second set of contacts 23 which are closed by the arm 22 1 whenever the system demand falls below a smaller predetermined value.

.The contacts 2| and 23 of the demand meter l8 are provided to energize suitable circuits whichautomatically act to transmit carrier currents in such manner as to add load to the system, or remove load from-the system, in such amounts as to-keep the total system-load substantially constant within certain limits: In certain situations it may not be desired to provide such a fully automatic system, and'I have accordingly provided hand operating means for the system. Where the manual arrangement aloneis desired. it is of course not necessary to provide the contacts 2i and 23 of the demand meter l8. When using the manual system, the operator determines when he wishes to remove load from the system or add load to the system by noting the position of the m'ember22 of the demand meter l8, or by any other suitable means.

In most cases, it will be desired to provide suchhand operatedmeans along with the fully auto-- matic arrangement, and I have illustrated the fully automatic transmitting arrangement in Fig. l as including manual operating means for accomplishing the desired results. A double pole, triple throw switch 24 is provided which has one movable blade 25 connected to one'terminal of the switch 24, the movable blades 25 and 28 make no connection. and the system can be operated neither manually nor automatically. In the upper position of the switch 24, the movable blade 25 is connected to the other terminal 39 of the source of operating potential, and movable blade 25 is connected through a normally open push button 29 to terminal 39 of the source of operating potential.

When the system is not in operation, the parts are as illustrated in the drawings. In order to operate the system manually, an operator first moves the switch 24 to the upperposition, thereby energizing the operating coil 21 of the circuit breaker I3 and starting the motor l2. After a short interval during which the motor I2 comes up to speed, the operator may depress the push button 29 to energize the operating coil 28 and close the circuit breaker l5, thereby energizing the power line H with carrier current from the generator l4. As explained above, because of the fact that carrier current receivers have certain manufacturing variations, and because operating voltage diiifers widely at diiferent points along the power line ll, individual carrier cur rent receivers operate at d flering times. Bv maintaining push button 29 closed for a suitable time, the operator may connect any desired number of loads to the line i l, or disconnect any desired number of loads from the line.

A preferred method of operation is, however,

I {or a half second and then leaves it open for a somewhat longer period, for example 1 /2 seconds, and if he repeats such operation, he can operate the carrier current receivers much more slowly than by keeping button 28- depressed continuously. He may, in fact, by suitably choosing the ratio of the time when he holds the push button 29 depressed to the time when he leaves it undepressed, operate the carrier current receivers with any desired slowness, so that he may discontinue. adding carrier current controlled loads to the system, or removing such loads from the system, whenever the indication of demand on the system justiiles it.

In the control system for automatically controlling the transmission of carrier current pulses for increasing or decreasing the connection of remotely controlled loads in accordance with indications of the demand meter I8, there is a master relay 30, two double coil, two-position relays 3i and 32, time delay relays u, 34, 35, and 36, and

a time switch 31. The relay 3| controls removal of the carrier current controlled load from the system. relay 8| prevents such loads from being re ved while the demand meter I8 is causing their connection to the line II. The second two-position relay l2 prevents the connection of such loads to the power line H while the demand meter I4 is causing the system to remove the remote loads from the line. The time delay relay 24 connects the generator l4 to the line H only after .the motor i2 has come up to speed. The time delay relay |4 prevents the demand meter II from causing connection of the remote load to the line H before the carrier current receivers have returned to a suitable condition to receive control pulses after having received a set of such pulses. The time delay relay prevents the system from transmitting pulses intended to connect remote loads to the system after all such loads have been connected. The time delay relay 3| prevents the system from transmitting additional pulses intended to disconnect remote loads from the system after all such remote loads have been disconnected. The time switch 21 is arranged to close and open a circuit alternately so as to transmit successive short pulses of carrier current in the process of connecting remote load to the power line H.

To connect the system for fully automatic operation, the double pole, triple throw switch 24 is moved to its lower position. In this switch position, when the operating coil 4| is energized, a circuit is, formed from one terminal 32 of the source of operating potential for the system through the contacts 34 of the master relay 8|, movable blade 24,.coil 21 and back to terminal 46 of the potential source and the circuit breaker I2 is operated to start the motor i2. When the arm 22 closes contacts 2| and contacts 42 0! relay ii are closed, the operating coil 4| 0! the master relay 3| is energized through a circuit extending (mm the terminal 4| 0! the source of operating potential through coil 4|, contacts 2| and arm 1|, and contacts 42 back to the terminal .3! of the source of operating potential.

When the system is in the-condition illustrated, the carrier current controlled loads are all con nected to the power line H, and the contacts 42 of the two-position relay 32 are open to prevent useless operation oi the system in attempting to connect additional remote loads to the line H. The contacts 42 of the two-positionrelay II are closed to keep the system in readiness for transmitting a pulse of carrier current to disconnect loads whenever the contacts 2| oi the demand meter l8 are closed by the arm 22 upon an increase in demand on the system.

When the demand on thesystem increases to an amount sufllcient to move the arm 22 to closing position against the contacts 2! of the demand meter l8, a .circuit is completed through coil 4| as explained above. As soon as the-coil 4i oi the master relay is energized, the normally open contacts 38 close, thereby completing a circuit from the terminal 39 of the source of operating potential through the contacts 3|, the movable. blade 25 of the switch 24, and the operating coil 21 01- the circuit breaker II to the other terminal 40 of the source or operating potential. The circuit breaker I3 is thereupon closed, and connects the motor I! to the power line ll so as to bring the motor generator set 12, i4 up to speed. A second pair of normally open contacts 44 or the master relay 2| simultaneously close. and seal in" the operating coil 41 of the master relay 3| through a circuit from the terminal 2| oi the potential source through the normally closed contacts 45 of the time delay relay 3|, contacts 44 and operating coil 4i 0! the master relay 3| back to the other terminal 4| oi the potential source.

Contacts 4! stay closed until all controlled loads are disconnected from the line H because the operating coil 4| 0! the time delay relay N is not energized until the circuit breaker ii is closed, and this relay 2| is so constructed as to open its contacts 4| only after being energized tor a period sumciently long that transmitted carrier current has caused all carrier current receivers to disconnect their associated loads from the power line H. In the case of the particular carrier current receivers described, this period -may conveniently be about forty seconds. The

master relay 40 thus remains closed for about forty seconds alter being operated, even though the arm 22 moves away from the contacts 2| of the demand meter 1|.

The contacts 2| oi the master relay 3|, upon being closed, also complete a circuit from the terminal 29 of the potential source through the operating coil 41 oi the time delay relay 33 to the other terminal 4| of the potential source. This time delay relay 3| has contacts 4| which are normally open, and is arranged to close its contacts 4| only alter the operating coil 41 has been energized for a period sufllcient for the motor generator set l2, l4 to come up to speed. It is usually suiilcient to allow about a five second interval for this operation.

After an interval sufllciently long for the motor generator set l2, l4 to come up to speed, the time delay relay 32 closes its contacts 4| and thereby completes a circuit from the terminal 2| 0! the potential source through the contacts 2| oi the master relay 8|, contacts 4| of the time delay relay IS, a pair of normally open contacts 48 of the master relay 3|, the movable blade 2| of the switch 24, and the operating coil 2| oi the circuit breaker ll back to the other terminal 4| of the potential source. The normally open contacts 4| of the master relay 8| were closed previously upon the energization of the operating coil 4i, so that closure oi the contacts 4| results in operation of circuit breaker II and connection of the When the contacts 48 of the time delay relay 33 close, another circuit is completed from the terminal 39 of the potential source through the contacts 38 of the master relay 30, contacts 48 of time delay relay 33, a pair of normally open contacts 50 of the master relay 3!), and operating coils 5i and 52, in parallel, of the two-position connection of the remote load thereto, even relays 32 and 3|, respectively, back to the other terminal 40 of the potential source. Energization of the operating coil 5| of relay 32 closes the contacts, 43 and puts the system in readiness for transmitting carrier current pulses to the receivers to cause them to connect load to the system. Simultaneous energization of the operating coil 52 of the relay 3| opens the contacts 42, thereby opening the circuit through the contacts 2| of the demand meter III to prevent further operation of the system in transmitting carrier current to the receivers to cause them to disconnect loads from the system.

After these operations, the system continues the transmission of a carrier current impulse from the generator. for forty seconds, until the time delay relay 33 opens its contacts 45 and deenergizes the operating coil 4| of the master relay 30, thereby breaking all operating circuits, including the circuits through which the operating coils 21 and 28 of the circuit breakers l3 and I5 are energized. The motor generator set l2, I4 is therefore disconnected from the power line II, the carrier current receivers have by such time disconnected all their associated loads from the power line H, and the transmitter is in readiness to respond to a reduced demand on the power line by transmitting pulses to the carrier current receivers to cause them to add increments of load to the power line.

Either of two conditions may obtain after the above described operation has been completed. If the increased demand on the system which'caused disconnection of loads therefrom was so great that, upon disconnecting all the carrier current controlled loads from the system, the arm 22 does not move to the left sufficiently to close a circuit through the contacts 23 of the demand meter l3, .the control system remains inactive. However, if the demand on the system which caused load disconnection was smaller, removal of the carrier current controlled load from the system may be sufiicient to make the arm 22 move to the left and close a circuit through the contacts 23.

In any case, the demand on the system must eventually become small enough so that the arm 22 closes the contacts 23. A circuit is thereupon completed from the terminal 39 of the po tential source through the contacts 43 of the two-position relay 32 (which contacts were closed during the preceding load disconnecting operation), contacts 23 and arm 22 of demand meter I3, normally closed contacts 53 of master relay 3. (which is now'deenergized), and operatingcoil 54 of time delay relay 34 back to the other terminal 43 of the potential source. The time delay relay 34 is so constructed that its norrier current receivers utilizes bimetal elements.

mally open contacts 55 are closed only after its operating coil 54 has been energized for a substantlal period, which may, for example, be as long as ten minutes.

The system is so arranged that closure of contacts 55 initiates operation of the system to connect the remote loads to the power line H. Because of the long time delay provided for the ;time delay relay 34, brief decreases in demand on the power line H are not effective to initiate '43 of the potential source.

56 and 31, of the time switch 31 and time delay though the arm 22 touches briefly the contacts 23 of the demand meter I3. Unless the demand remains low enough to keep arm 22 against contacts 23 until relay 34 acts, the system does not add load to the power line.

The delay in the relay 34 also serves another purpose, namely, to prevent the transmission of carrier current pulses to the carrier current re-' ceivers immediately after they have received a pulse which has caused them to disconnect their associated loads from the power line H. As ex plalned hereinafter, the preferred type of carwhlch depend on heating for their operation, and a short time should be provided after each operation of the blmetal elements to allow them to cool and return to a responsive condition. That is, if the arm 22 should move to the right in responseto increased demand and touch contacts 2| to produce operation of the system to disconnect all remote carrier current controlled loads from the line H, and immediately there I after if the system demand should drop sufficiently to move the arm 22 to the left to close contacts 23, the time delay of the relay 34 assures that no carrier current is transmitted to the receivers until they are restored to a receptive condition for reconnecting loads to the line II.

If, therefore, the decreased demand on the line H remains at a sulhciently low value to keep the arm 22 against the contacts 23 for a period longer than that for which the relay 34 is made to remain open, the contacts 55 close and complete a circuit from the-terminal 3,9 of the potential source through the contacts 43 of relay 32, contacts 23 and arm 22 of demand'meter 13, contacts 53 of the master relay 30, contacts 55 of the time delay relay 34, movable blade 25 of the switch 24, and operating coil 21 of the circuit breaker l3 back to the other terminal The operating coils relay 33 respectively, are connected in shunt to the operating coil 21 through the movable blade 25 of the switch 24, and are, therefore, energized at the same time through this circuit.

When the operating coil 21 is energized, it operates the circuit breaker l3 and starts the motor generator set l2, l4, and after a suitable interval the time delay relay 33 closes its contacts 43 to complete a circuit from the terminal 33 of the potential source through contacts 43 of relay 32, contacts 23 and arm 22 of demand meter I3, contacts 53 of master relay 3!), contacts 55 of time delay relay 34, contact 13 of time delay relay 33, a pair of normally closed contacts 56' of the master relay 3!! (which is now in unenergized position), and the operating coils 51 and 53, in parallel, of the relays 3i and 35, respectively, back to the other terminal 40 of the potential source. The operat-= ing coil 51 of the relay 3| closes the contacts 42' (which were left open after the preceding operation of the system in disconnecting all remote loads from the power line H), so that closure of the contacts 2| of the demand meter 18 .by the arm 22 can immediately initiate another are connected, the operating coil 60 of the relay 32 is connected in parallel to the operating coils 51 and 58 of the. relays 3| and 85, so that the contacts 43 of the relay 32 areopened, thereby opening the circuit including contacts 23 of de= mand meter l8, and preventing the system from sending any more carrier current pulses of the type which cause the carrier current receivers to connect loads to the power line it. in this particular system, it is convenient to make the time delay of the relay 35 about thirty seconds, as will be explained hereinafter.

During the time when the contacts 23 are closed by the arm 2201 the demand meter 58, and the time delay relay 35 is moving'toward the position where its contacts stare closed; the'time 1 i switch Bl remains in operation. It is so con-; structed that, while its operating coil 56 is energized, it continually makes and breaks a cir-- cuit in shunt to the normally open contacts 39 "or the master relay it (which is deenergized).

The time switch 31 may be conveniently arranged, as shown, to have a movable arm at which is rotated bythe operating coil 56 across a plurality of contacts 82 arranged in a circle, whose center is on the axis ofrotation or the arm 6!. The contacts 62 and the spaces theretinues to remain low and the arm 22 remains against the contacts 23, the carrier current re- 2,297,380 when the contacts 59 close after all such loads line H naencantation of the remotely controlled loads to' the line.

Nowit the demand on the power line ll conceivers-progressively cont act more and more of their associated load} to the power line H, and all suchloads eventually become connected withclosure, the contacts 59 orv the relay 35 close to in aboutf25 seconds after contacts 48 or the relay 33 have'closed. Thirty seconds after such energize the operatingcoil. Goof the relay 32 and open'contacts 43, thereby interrupting the circuit through the contacta 'if ncl preventing further transmission orf'short itarrier current pulses.v such-transmission is c longer desirable,v because all thew-remlitedoads have been I connected to the power line' H.

between may be proportioned in any desired manner to provide that repeated short pulses of carrier current are transmitted over the power line H with any desired spacing therebetween, H

so as to increase by any desired amount the total length of time required for the carrier current receivers to respond to such pulses in connecting their associated loads to supply line ii.

The circuit whichis repeatedly completed and interrupted bytime switch 31 as long ascontacts 23 are closed may be traced from the terminal 39 of the potential source through contacts 53 of relay 32 (which contacts. are not opened by the time delay relay 35 for 30 seconds), contacts 23 and arm 22 of demand meter 58, contacts 53 of master relay 30, contacts 55 of relay 35, contacts 38 of relay 33, contacts 52 and arm di or time switch 3'5, movable blade 26 of switch 26, and operating coil 2% ct circuit breaker 55 back to the other terminal at of the potential source.

As long as the arm 22 remains against the contacts 23 (until contacts 59 of the time delay relay 35 close), the arm ti of the time switch 3? repeatedly energizes and deenergizes the operating coil 28 of the circuit breaker i5, so as to connect and disconnect the generator l6 from the power line M. This results, as long as the demand is suficiently low, in a series of carrier the arm 22 from thecoi ita' It may, however, happen that, as the carrier current receivers slowly connect. their associated loads to the powen-line II in response to repeated closures of Pievc: uit fbreaker ii, the demand on the powel line ll. ,rises"'s ,uihciently to move '23; Attire moment of this opernng all circuitsithrough the 'control system are opened, including the circuits through the operating coils 21, 28, 54, ll, 56, 57, and 58. The motor generator set [2, It therefore stops, the time switch 3lstops, the time delay relays 33, 34 and 35am released to their initial positions, and the remote loads which have so far I been connectedto the powerline H- remain connected thereto, whileno more loads are added.

It the demand on the system. thereafter increases to the point at which the arm 22 closes the contacts 2|, the previously described operation is initiated, in which a long carrier current pulse is transmitted, and all the remote loads are disconnectedfrom the power line H. The load disconnecting circuit may be completed through 7 contacts 2| because contacts 42 of relay 3| were closed immediately when loads were connected to line H after a preceding disconnecting operacurrent pulses being transmitted over the power 'line H, and these pulses afi'ect the carrier current receivers in the same manner as if a continuous pulse were transmitted, except that it takes a somewhat longer time to produce the same efiect. For example, if the circuit breaker tinuous carrier current puise were transmitted.

By thus slowing down the action or the carrier current receivers in connecting their associated ioads, the demand meter I8 ismade better able to respond to changesin demand on the power It may happen that the demand does not thus increase but again decreases. Then, the arm 22 again touches the contacts 23 of the demand meter 58, and if the demand remains at a low value for a period long enough to close the contacts of the ten minute delay relay 3, the entire sequence of operation begins anew to start the motor generator set l2, H, and to connect additional loads to line H. Such operation eventually causes additional carrier current receivers to. connect their associated loads to the power line H, thereby causing the demand to increase again; If this action be continued past the time when all the carrier current receivers have operated to connect their associated loads to the line H, and long enough for the time delay relay 35 to close its contacts 59, as explained above, the operating coil is energized and opens the contacts 43- of the relay 32, thereby disabling the contacts 23 of the demand meter 88 from completing a circuit through the control system to cause any further operation.

Although the automatic system has been described as having no means to disconnect loads progressively fromthe line, as -it has means to connect such loads progressively to the line, such progressively disconnecting means may ob viously be utilized, if desired. The progressive disconnecting means is exactly like the connecting means and transmits pulses effective to disconnect loads slowly from line ll. It is pre= ferred at present'to the system as illustrated to avoidjadditional complication of parts and tov retain certain advantages in connecting loads necessary lac-decrease loads gradually because, as explained previously, less total load must be dis connected than must later be connected, and becauseloads are progressively connec'tedto the first at'points oi high systemvoltage. It is not" 7 fen-ed because line surges; due to switching and the'likacannotcauseittooperater.

' As mentioned 'hereinbefore, a preferred typeof carrierifcurrentreoeiver is described in Letters Patent No. 2,064,644-issued to me .on December 15,1936, and asslgnedto-the same assignee as the present application. .Such areceiver is illusline in any necessary amount almost immediately aftertheir total disconnection, if such reconnection'is necessary to maintain optimum demand on the line at all times within the capacity of Y the carrier controlled load tovary such demand.

As explained previously, the fact that different carrier control receivers connected to the power line ll respond to carrier current impulses of different duration may be attributed, not only to the fact that there are manufacturing variations in the receivers, but also to the fact that the re- .ceivers are connectedat points on the power line H where there are differing voltages. The differing voltages on 'the'line may'even be the principal factor in producing the varying response times of receivers. On some secondary feeders,

for example, there may be voltages as low as llO volts. On other secondary feeders, which are lightly loaded the voltage may be as high as 125 or 130 volts. r

In short, carrier current receivers on high volt age feeders generally operate in shorter time than such receivers on low voltage feeders. A

load connected at a high voltage point of a nor mal power transmission system generally pro formers and other equipment, but also in smaller copper loss in the power line H and the feeders which form a part thereof.

These advantages, which are related to the fact that carrier current receivers tend to operate flrst at high voltage points of the system, also .accrue in a system in which the varying time of operation of receivers is caused by carrier voltage variations from point to point of the system. Carrier voltage variations generally correspond ,to power voltage variations. It is preferred, though, to utiliz receivers in which the operating time is dependent on power voltage variations.

It is to be understood that it is within the scope of my invention to utilize any type of carrier current control receiver which responds only after receiving a carrier current for a substantial time. It is preferred, however, to use such a receiver which resets each time after it receives energy. That'ls, it is preferred to use a receiver which returns to a'normal, or initial, starting condition within a short time after the reception. of any carrier current impulse, Such receivers may be of the thermal type, in which a switch is operated through the medium oi a bimetal strip to which heat is applied during the reception of a carrier current impulse. After an impulse is no longer received, the bimetal strip cools oil and the receiver returns to its initial starting condition. This type of receiver is pretrated' in Fig. 210i the drawingsaccompanying the present application, in which a. portion of the power line H is illustrated. Several carrier current receivers, each shown as a rectangle ll, are connected to the line H. One of these-rec: tangles is formed by dashed lines, and includes a 'load deviceli connected to beenergized from 'power line H through a'power transformer l2 and a switch it The switch 13 is'of' the liquid-contact type and is completely described and claimed in Letters Patent No. 2,101,092, issued on December 7, 1937, to John lLjlayne, Jr., and assigned to the same assignee as the present application. Briefly, the switch comprises apair of metallic hemispheres separated by a disc of refractory material, and

by a fillet of thermoplastic insulating material which is fusion weldedto the rims of the disc and of the two hemispheres, thereby sealing the container thus formed. A body of liquid con ducting material is sealed within the hemispheres and serves to make and break the electric circuit therebetween through an aperture in the disc of refractory material when the switch is moved between'two operating positions.

Associated with each device it is means for storing the energy of the pulses sent out over the lines H until a predetermined value is reached, at which time the switch '13 will be operated. In other words, the energy of the transmitted pulses is stored for a time interval, the duration of which is a function of the amount of stored energy required to operate the device.

In the illustrative form of my invention, the switch is thermally operated and has substantial heat-storage capacity. As previously explained, the diiferent switches have different storage capacities so that the device will not be operated until there is transmitted an impulse of sufllcient duration or a sumcient number of successive impulses to increase the stored energy. such as heat, in the storage means or device to the value necessary for operation. The switch it is carried by a yoke 14, pivoted on the free end of a supporting member 1i, and actuated by the movable free end of a bimetallic member II to which heat is applied by an electric resistance heater H. In the position shown, the switch 11 is in circuit interrupting position. Upon energization of the heater 11, the strip l0 bends to the right and allows the yoke 14 to move clockwise. $uch movement of the yoke 14 turns the switch 13 into circuit completing position, and connects the load 1 ii to the power line H through the transformer 12. It is to be understood, of course, that the load 1 i, which is indicated as a lamp, may be any load on the power line I I for which remote control is desired. As explained previously, particularly good results are obtained with a carrier current control system arranged in accordance with my invention when the load H is an elec .tric water heater or the like load which acts to store energy.

Electric energy is applied to the heater 11 from a transformer 18, which is connected across the secondary of the transformer I! through contacts "i! of an electromagnetic switch having an operating coil 8|. A series resonant circuit including a condenser 8| and an inductance 82 is connected in shunt to'the secondary of the transformer 72, a

and is tuned to the frequency of carrier current transmitted irom the generator M of Fig. l. A full wave rectifier circuit including rectifying means 83 is connected across the inductance 82, p

to close contacts "and transmit power current from the power line II to the heater As explalned above, when a smallan ount of heat, corresponding to a short impulse'fiif' 'carrier current, which, for example, lasts for three to six seconds, is applied by the heater 11 to the bimetallic strip 18, the strip moves to the right, thereby .pull the yoke 14 counterclockwise around the bimetallic strip 15' back to the circuit interrupting position of the switch 13.

It' is apparent from the description of a power system arranged according to my invention with a carrier current control system providing accurate control of certain loads on the system, that an improved load factor may be obtained for the entire power system by connecting just enough of the controlled loads to the system at any time to keep power demand at annoptimum value.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within removing support from the right end or the yoke I l4, and allowing it to move clockwise and close the switch 13.

If a longer carrier current impulse be transmitted over the power line I I, similar operations ensue, but the heater 11 applies a larger amount of heat to the bimetallic strip 18,.so that it moves farther to the right and eventually engages the reset trigger 88, which is connected pivotally to the yoke 14. After the carrier current impulse has ended and heat is no longersupplied to the bimetallic strip 16, the strip moves to the left, and, through the medium of the trigger 8|, pushes the yoke l4 back in counterclockwise rotation to interrupt the circuit through the switch 13. At

of said pulses being shorter than the length rethe end of travel of the bimetallic strip 18, its

upper end again rests under the end 01' the yoke M to maintain it in its counterclockwise position.

In Fig. 3, the thermally operated switch 13 with its associated operating parts is shown in somewhat greater detail. It is desirable in a thermal relay of this type that ambient temperature changes be prevented ,tro'm effecting relative movement between the upper tree end or the bimetallic strip 78 and the yoke 14. To this end the supporting member 15 is made'of bimetallic material, so that its free end, which supports the yoke H, moves in the same direction and in the same amount as the endor the bimetallic strip It in response to changes in ambient tempera- Suitable "adjusting means comprising a U- shaped member 85, a stifi resilient backing strip 86, and a screw 81, are provided for changing the relative positions 01 the free ends of the two bimetallic strips 15 and 16, thereby to change the energization period necessary to actuate the bimetallic strip 16 between its operating positions. Manual control means are provided to operate the switch between its two positionsfor testingor other purposes. Such means comprise a pair of operating rods 88 and 89 which may conveniently extend outside the case of the-thermal relay. When the operating rod 88 is pulled downthe true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a carrier current control system having a plurality of carrier current receivers or a type which operates to effect a desired control operation in response to reception of a carrier current pulse of substantial duration, the difierent receivers being operative to effect their respective control operations in response to reception of carrier current pulses of different durations, the method oi operating any desired number of such receivers which comprises transmitting a succession oi pulses of carrier current to said receivers, each quired for operation of any or said receivers, the length of said pulses with respect to the length of periods without carrier current transmission 'betweensaid pulses being sufiiciently great to operate a desired number of said receivers atter a number of such pulses is transmitted.

2. In a carrier current control system having a plurality of carrier current receivers of a type which operates to efiect a desired control operation in response to reception of a carrier current pulse or substantial duration, the different receivers being operative to effect their respective control operations in response to pulses of such carrier current of difierent respective durations, the method of operating any desired number of such receivers which comprises transmitting to said receivers a carrier current pulse of sufficient duration to operate any desired number of said receivers after such pulse is transmitted.

ward, it is arranged through the medium of a' member 98, which'isfastened to the bimetallic strip 15, to pull such strip to the left and release the yoke M from the upper free end of the bi- 'metallic strip 18. Thereu-pon the switch 73 is turned to its circuit completing position. When the operating rod 88 is pulled downward it is arranged, through the medium or a spring 9|, to

3. In'acarrier current control system having a plurality or carrier current receivers or a type which operates to eflect a desired control operation in response to reception 01 a carrier current pulse of substantial duration, said receivers being operative in response to potentials on said system and being located at points of said system having different potentials, whereby, and by reason of unavoidable manufactu ng variations, the diflerent receivers are operative to efl'ect their respective control operationsin desponse to pulses of carrier current or diflferent respective durations, the method of operating any desired number of such receivers which comprises transmitting to said receivers a carrier current pulse of suflicient duration to operate any desirednumber or said receivers after such pulse is transmitted g 4. Incombination, inapower transmission sys- .temhaving loads which may be disconnected from said system during peak demand thereon,

means for individually controlling the connection of such loads to said power system, and means responsive 'to the; demand-on said system for controlling said connecting means to connect the associated loads progressively to said system as the'demand on said system fails. thereby to improve the load riactor oi said system.

5. In combination, in a power transmission system having loads which may be disconnected irom said system during periods oi maximum demand thereon, means ior individually controlling the'connection and disconnection of loads irom said system, means responsive to e demand on said system ior operating said connectingmeanstodisconnectsaidloadsiromsaid system upon an increase in the demand thereon, and means responsive to decreasing demand on said system ior connecting said loads to said mtom progressively as the demand thereon decreases, whereby the load iactor otsaid system is improved.

6. In combination, in a power on system having loads which may be disconnected iromsaidsystemduringperiodsoimaximumdemand thereon, a carrier current control system associated with said transmission system and comprising carrier current receiving means associated with each of said loads ior controlling individually the connection oi said loads to said system, each oi said receiving means being eiiective to produce a control operation only after reception of a carrier current impulse oi diiierent duration, and means responsive to demand on said system ior transmitting carrier current to said receiving means to eiiect progressive connection oi said loads to said system as the demand on said system decreases.

'I. In combination, in a power ton system having loads which may be dismnnected therefrom during periods oi high demand thereon, means ior controlling individually the connection oisuchloadstosaidsysteminresponsetothe reception oi carrier current ior a substantial time, each oi said means being eflective to produce a control operation upon reception at carrier current ior a diiierent time, and means mar/are sive to changing demand on said system ior transmitting carrier current thereover to said controlling means, said transmitting means being operative to transmit carrier current only until said controlling means have eiiected changes in the connection oi a portion oi the loads on said system such that the resulting demand on said system coniorms to a predetermined desired demand.

8. In combination, in a power transmission system having loads which may be disconnected thereirom during periods oi high demand thereon, means ior controlling individually the connection oi such loads to said system in response to the reception oi carrier current ior a substantial time, each oi said controlling means being eiiective to connect the associated load to said system upon reception oi carrier current ior a diiierent time, and means responsive to decreasing demand on said system ior transmitting successiveshort impulses oi carrier current to said controlling means only until a portion oi said controlling means has operated to connect a suiflcient number oi loads to said system to increase the demand thereon to a predetermined value, the length oi such short successive impulses oi carrier current being suiiicient with respect to the length oi intervals therebetween to operate said controlling means aiter reception oi a norm her oi such short pulses.

9. In combination, in a power transmission system having loads which may be disconnected therefrom during periods of high demand thereon, means'ior eiiecting individually the connectionoisaidloadstosaidwsteminresponseto oisaidloadstosaidsystemwheneverthedemandonl said system rises above said predetermined V8 6.

10. In a power transmission system having loads which may be disconnected therefrom during periods oi high demand thereommeans-w sponsive Jointly to system voltage and to carrier currenttransmittedthroughsaidsystemiorconnecting such loads to said system; said controlling means being connected to said system at points oi diiiering system voltage thereby to cause iast operation of said controlling means at points 0!- high voltage and slow operation of said controlling means at points oi low voltage, and means responsive to decreasing demand on said system for transmitting carrier current'over said system to said controlling means to eiiect pve individual connection oi said loads to said system, said controlling means at said high voltage points being automatically first selected for operation in response to such transmitted carrier current, whereby loads are first connected to said system at high voltage portions thereof.

11. In a remote control system having a pluralityoddevicesoiwhichanydesirednumberis to be operated, means to supply control pulses to said devices, each of said devices having means tostoretheenergyoisaidpulsesioraninterval whose duration is a iunction oi the amount oi smred energy and to operate the respective device when energy stored in the corresponding storage means attains a predetermined value,

said predetermined value being diiierent in the diiierent devices, the method oi operating any desired number oi such devices which comprises supplyingtoalloisaiddevicesasuccessionoi control pulses spaced in time by less than said interval, the succession including a number 01 pluses sumcient to increase the stored energy in the respective storage means to a value as mt as that value of energy storage required to operate the desired number oi devices.

12. In a remote control system having a plurality or devices oi which any desired number is to be operated, means to 81mph? current to said devices, each 01' said devices having means to store the energy oi said current and operate the respective device when energy stored in the corresponding storage means attains a predetermined value, said predetermined value being dilierent in the diiierent devices, the method oi operating any desired number 01 such devices which comprises supply current to all oi said devices ior a time suiiicient to increase the stored energy in the respective storage means to a value as great as that value oi energy storage required to operate the desired number oi devices.

operative in response either to continuous energization for a predetermined period or to in .termittent energization for a longer period to operate the respective switch, said predetermined period and said longer period being different for the different switches, the method of operating any desired number or said switches to control the connection or any desired number of said loads from said system, which method comprises supplying to all of said control means successive pulses of sufiicient number to cause operation of a desired number less than all oi said switches.

14. In a remote control system having a plurality oi remotely controlled switches operated in response to pulses received from a common point, each of said switches having means associated therewith to store the energy of said pulses for an interval whose duration is a function or the amount or stored energy and to operate the respective switch to one position when said stored energy exceeds a certain predetermined value and to the other position when said energy exceeds a different value, said predetermined values being unavoidably different in the diflerent means, the method of operating any desired numi ber of such switches which comprises supplying to all of said means a succession of pulses spaced apart in time by less than said interval, the number of pulses being determined in accordance with the number of said switches to be operated.

15. In a remote control system for a plurality of loads on a power system from which such loads may be disconnected during periods of peak demand, each of said loads being connected to or disconnected from said power system by a thermally actuated switch, each of said switches having substantial heat storage capacity whereby actuation thereof is delayed for a substantial time after a control impulse is applied to such switch, the difierent switches being responsive .to such control impulses of different durations to connect or disconnect the associated loads, the method of adiusting the number of such loads connected to said power systems which comprises transmitting a control pulse to all of said thermally actuated switches of such duration that a desired number less than all of said switches are actuated.

JOHN L. WOODWORTH.

' -Patent 10. 2,297,580.

' CERTIFICATE OF CORRECTION. V

1 September 29, 19!;2.

JOHN L. 'NOODWORTH.

I 'It is he'reby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 8 sec ond column line' 59, claim 1,1 before number' insert "corresponding";

line 65, claim}, for 'desponse" rend e--response--; and that the sold Lot- 'ters Patent should be read with this correction therein that the sanie may conform to the record of the case in the Patent 0ffice.

Signed and sealed thislOth day of November, A. D. 19141.

. Henry Van Arsdsle,

(Seal) I r Acting Commissioner of Patents.

' 'Pat ent no. 2, 97,38

- CERTIFICATE OF CORRECTION. w

' September 29, 1&2..-

JOHN L. woopwon'i'fi.

K 'It is ho'reby cortii-ied that error appear in the printed specification of the above numbered patent requiring correotion'as follows: Page 8 second oolumxh line' 59, claim 1,-. bofore "number" insert "corresponding"; line 63, claim}, for deaponse' rend .--response--; and that-the sold Let'- -,-;-tora Patent should be regd with this correction thorein that tho sanie may 'conforni to the record of the case in the PatentOffice.

Signed and sealed this 10th day of Novembor, A. 1), 191,2.

Hnry Van Arsdale,

(Seal) Acting commissioner of Patents. 

